Compound venturi carburetor



C. L. RAYFIELD COMPOUND VENTURI CARBURETOR am, 2i,-a:92. 1,6m,453

Filed Oct. 28, 1922 2 Sheets-Sheet 2 Figure 1 on As shown ontheldrawingsi-Q u The bodyofthezcarburetor'of this. inven- -tioncomprisesa float chamber 1,*an. airinso.

for regulating the gasoline feed to the intermediate speed nozzle;

Patented Sept. 28, 1926.

v UNITED STATES CHARLES L. RAYFIELD, OF CHICAGO, ILLINOIS, ASSIGNOB T0 BENEKE MANUFACTUR- ING COMPANY, OF CHICAGO, ILLIN OIS, A CORPORATION OF ILLINOIS.

COMPOUND VENTURI CARBURETOB.

Application filed October 28, 1922. Serial No. 597,457.

This invention relates to a compound Venturi carburetor having few moving parts and capable of adjustment for best performance over a wide range of speeds.

It is an object of this invention 'to provide a carburetor that can be adjusted to give a progressively richer mixture as the throttle is closed, thereby meeting the requirements for satisfactory performance of an internal combustion engine.

It is a further object of this invention to provide a carburetor free from the requirements of manual adjustment after the adjusting means have been set for the best performance of the engine to which the carburetor is attached.

It is an important object of this invention to provide an improved carburetor having a fixed venturi for the intermediate speed ranges and a movable venturi for the higher speed and load requirements.-

It is a further important object of this invention to provide a compound--fuel -nozzle, the main nozzle of which is controlled by the movable venturi and the other nozzle by the throttle in such a way that as the demand on the carburetor increases the second nozzle will-have its fuel supply restricted as the mainnozzle is opened. v p

Other and further important objects of this invention will be apparent from the disclosures in the drawings and specifica-'- tion The invention (in a preferred form) is illustrated on the drawings and hereinafter more fully described.

On the drawings: .Figure 1 is an elevation of my carburetor with parts shown in section.

Figure 2 is a top plan .view of the same.

Figure 3 is a section at right angles to the center line of the chamber. Figure 4 is-an enlarged sectional detailof the compound nozzle shown in Figure 1.

Figure 5 is a detail of the needle valve gure 6 1s=a sectionalviewyon.the '1i (H-f Figure 3. 1

letjchamber 2, ca mixing chamber 3, and a} dash pot chamber 4. Attached to the upper end of the mixing chamber 3 is a member 5 carrying the butterfly throttle valve 5 and a flange 6 to mate'with the flange on the intake manifold of the motor. Fuel is supplied to the float chamber through a strainer 7. The float chamber mechanism and the gasoline strainer do not comprise part of the present invention and are so well known that no descriptionthereof is considered necessary.

A centrally apertured partition 8 is' formedbetween the mixing chamber 3 and dash pot 4. A. vertical tube 9 supported over the aperture forms the outer or intermediate speed nozzle and is held to the partition by an inner vertical tube 10, forming the high speed nozzle, which has a threaded connection 11 at the top engaging with. the tube These tubes -have flanges 12 and 13 en aging on the top and bottom of the partition boss 14: and forming a chamber or well 15 within said boss 14. The external diameter of the tube 10 is less than the internal diameter of tube 9 forming a passage 16 from the well 15 up to the threaded con nection 11. A plurality of passages 17 are provided in tube 9 leading outwardly into the mixing chamber just below the threaded connection 11. p 5

A small venturi 18. is' secured around the tube 9 to cause suction'on the passages ,17. One side of this venturi is'cut away below the jets to alldw admission of air from the chamber 2, which passes up the annulanpas-f sage 19 surrounding the-tube 9. The venturi has outward passages 20 atits throat correspending in position to the passages 1.7 in tube 9 to permit atportion of the f 1101 spray 'to pass therethrough when the -throttle is completely closed., This venturi is provided with .an' outwardly extending apron 21 which" will be reterred to hereinafter.

-. The inlet of air for high S gad'is-eontrolled b 'a Venturi tube 22s'l1dable' in. the;

mixing c amber and normal] s ated on the apron 21 of'thesmall venturi. 18 at low and intermediate speeds, therebypreventing; the

The venturi;; -22:,,is1 ,eastp with-thin -walls for thereon to properly center .said venturivin g-lightness-so-that the outside-takes the'iorm of the inside'and guide fins 22e-t'are-.formed the mixing chamber. The. venturi: made li t ei fiL-th" s m ie -nenr Sirl. 1

, chamber and rotating the piston and exten up will tend to lift the yenturi and allow air to pass therethrough around the apron 21 on the small stationary venturi 18. The

'trols the outlet of fuel therefrom by means of a tapered portion 28 on said pin. An extension 29 of said pin passes downwardly through said tube and the lower end thereof is secured to a late 30 on the lower side of the dash'pot p1ston31 slidablymounted in the dash pot chamber 4. The plate 30 covers a central aperture 32 in. the piston 31 and is loosely held to the piston by a member secured 'to'the plate 30v and engaging the top of the piston by means of lugs 33 which are given a slight clearance from the piston so that a downward movement of the venturi and meteringpin will move the plate 30 away from th'e'piston allowin escape of the liquid below the piston throug the aperture 32. On the other hand, upward'movement of the venturi will be hindered by the plate which is then lifted against the piston, sealing the aperture. i

' The controllin l effect of the tapered metering pin 27 is regulated by adjusting its position-in regard to the threaded boss 25 whichfmay be effected by removing aclosure 34 from the bottom of the dash pot sion of the pin. In order that the adjustment may be locked a set screw 25' is inserted in the threaded boss 25 in line with the meteringpin so that the set screw may be set up against the head of the pin. Liquid fuel is supplied to the dash pot from the float ehamberl through the passages 35,'

36 and.37 the latter of which opens into the well or recess 38 above the point of the needle valve 39, this recess 38 communicating with the float chamber 1 as shown in dotted lines-in Figure 3. The dash pot is thus the, source of'the fuel supply for the high speed nozzle'10. controlled'by the metering pin 28. It will-l bel apparent that the check upon the: upward movement of the dash pot piston 31 provided by the'plate 30 converts the piston into a pump to increase the flow of fluel'through the high speed nozzle thus temporarily giving a richer mixture that is proportional to the sudden ness of the demand; in other words, supplying a richer mixture for, purposes of sudden acceleration. I

The needle valve 39 is mounted in a pas 'saged boss 40 on the'side of the float chamber. The passage or recess 38 has a smaller passage 41 leading axially therefrom and communicating through passage 42 with the annular well 15 formed by tubes 9 and 10 which feeds the intermediate nozzle 19. The flow of fuel through these passages is controlled -by the adjustable spring loaded needle valve 39 which seats on the shoulder formed by passage 41 and recess 38. The butterfly throttle shaft has a cam 43 mounted thereon which actuates a bell-crank lever 44 with a bifurcated end engaging around a block 45 upon the needle valve 39 above the cap 46 which closes the recess38. The cam and bell-crank are arranged to lift the needle valve 39 as the throttle is closed thereby supplying more fuel to the well 15. The block 45 is held on the threaded needle valve stem by a knurled nut 39 which allows adjustment of the lift of the needle valve and which is locked by a detent held in a boss on the block 45.

Two sources of fuel are provided for idling speeds; a passage 47 leading from the dash pot chamber to passage 48 leading up through a boss on the side of the mixing chamber and into the member 5 where it communicates with a smaller passage 49 opening into the intake passage above the throttle, as shown in Figure 3. The second source consists of a tube 50 leading from the member 5 down inside the venturi 22 end-' ing near an aperture 20 through the station ary venturi 18 where it picks up a mixture of fuel and air. The upper end of the tube 50 communicates through passages 51 and 52 with the intake passage above the throttle as in the first case. I I.

As shown in the drawings, the air inlet is provided with the usual choker butterfly valve, with the usual arrangement of lever and boss for Bowden wire control.

Theoperation is as follows: The tubes 9 and 10 form a compound nozzle wherein the outer tube 9 supplies fuel to the stationary venturi 18 that cares for the intermediate speed range when the large venturi 22 is seated on the apron 21 of the stationary venturi. Under such conditions, the throttle will be partly closed and the cam 43 and bell-crank 44'will have lifted the needle valve 39 thus feeding more fuel through this nozzle. Opening the throttle will partly close the needle valve cutting off most of the fuel to nozzle 9, while the increased suction on the mixing chamber lifts the large venturi 22, the metering pin 28-and the dash pot piston 31 which momentarily e'ects a surplus of fuel from the nozzle '10 or acceleratingfpurposes, and thereafter supplies most 0 the fuel for open throttle operation. The fuel supply through metering vpin and the greater the on the movable venturi the higher it lift! no with consequently greater passage for air and a correspondingly greater amount of fuel is admitted through the increased nozzle opening.

As the throttle is closed, the suction below the throttle decreases, allowing the large venturi to drop on the apron 21 cutting ,ofi' both air and fuel. At the \same time, the intermediate nozzle between tubes 9 and 10 gets a greater supply of fuel due to the needle valve 39 bemg raised by the cam and bell-crank, so that the mixture grows richer as the throttle closes. At idling speeds, the suction above the throttle brings the idling well into play providing a still richer mlxture.

It is therefore apparent that no adjustments for different speeds and loads will be necessary after the metering pin and needle valve'have once been correctly adjusted as the caburetor supplies a richer mixture for low ower requirements, thus rendering a cholie unnecessary except for starting under severe weather conditions.

I am aware that numerous details of construction may be varied through a wide range without departing from the principles of this invention, and I therefore do not purpose limiting the patent granted, otherwise than necessitated by the prior art.

I claim as my invention 1. In a carburetor, a fuel supply chamber, a dash pot chamber communicating therewith, a mixing chamber, an inner nozzle 0 ening into the mixing chamber and the dash pot chamber, an outer nozzle also opening into the mixing chamber and having a source nozzle, a piston in the dash pot chamber and a connection between the fuel controlling means and said piston.

2. In a carburetor, a fuel supply chamher, a dash pot chamber communicating therewith, a fuel outlet Well, a needle valve therein, a tubular high speed nozzle in communication with thedash pot chamber, an annular intermediate speed nozzle surrounding the high speed nozzle and in communication with the fuel outlet Well, a stationary venturi surrounding the intermediate speed nozzle, a low speed fuel passage between the exterior of said stationary venturi and the discharge side of the throttle valve. passages through said stationary venturi supplying fuel to said low speed passage, a

high speed venturi surrounding said stationary vcnturi and slidably mounted in the mixing chamber, means connected to said,

slitlable venturi for controllin the amount of fuel discharged from sai high speed nozzle, a piston in the dash pot chamber, and a connection between the fuel controlling means and said piston.

in testimony whereof I have hereunto subscribed my name.

CHARLES L. RAYFIELD. 

